I have a 93 Merc 135 EL/PTO and am having a rather strange issue. I was out on the lake cruising at about 30 MPH or so and got the Beep, Beep, Beep alarm. I know that this is the oil pressure alarm so I immediately shut down and was towed to my trailer by some good samaritans. Upon examination, I noticed that the small reservoir on the outboard (not the main oil tank on the boat) was full. When I removed the cap of the reservoir and the plunger dropped, the alarm stopped. Obviously this is backward of the way the system should operate (the alarm should sound if the plunger drops showing a low oil situation). I took it to a Merc. service center, and they had three guys trying to diagnose the problem for four hours. They tried a new cap on the reservoir and did additional diagnostics to try to isolate the problem, but were unable to. I am a good mechanic, but outboards are a new world for me. Any advice would be much appreciated. I am a new poster here, but have read and learned much from this forum.
Thanks for your help. -Dan
Thanks for your help. -Dan